In certain manufacturing processes, there is a need to align two surfaces so that they are truly parallel to each other (within a prescribed tolerance factor). For example, when placing a very delicate planar object, such as a semiconductor chip, onto a planar substrate, such as a silicon or diamond mount, it is important that the chip be substantially parallel to the mounting substrate during placement. If the chip is not maintained parallel to the mounting substrate during placement, the chip may crack or otherwise become damaged when brought into contact with the substrate.
In the past, alignment of two surfaces has been accomplished with the aid of a laser interferometer. While the laser interferometer is capable of detecting the degree of parallelism of two surfaces quite accurately, the laser interferometer is nevertheless costly and complex to operate. Moreover, as its name implies, the laser interferometer contains a laser whose use is subject to many safety precautions. Consequently, such laser interferometers cannot always be readily employed in a factory environment to make on-line parallelism measurements during the alignment of two surfaces.
Thus, there is a need for a technique for aligning two surfaces to achieve substantially true parallelism therebetween without the need for a laser interferometer.